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FH680V-BS29
#1
ILENGINE
ILENGINE
Here is one for you guys to ponder. Fresh RN14YC spark plugs, new OEM ignition modules, valves set to .006, and freshly rebuilt carb. Engine will start within about 4-6 revolutions cold, but after running 10-15 minutes won't start with or without choke hot, And will not fire with addition gas dumped into the intake. And the tip of the afterfire solenoid has been removed. And gas is known to be fresh.
#2
T
txmowman
T
txmowman
Well, first of all, all cutting the tip off a fuel solenoid does is make it a junk part.
Assuming the fuel dumped into the intake is actually making it to the cylinders, you likely have a sticking valve would be where I would check.
Assuming the fuel dumped into the intake is actually making it to the cylinders, you likely have a sticking valve would be where I would check.
#3
ILENGINE
ILENGINE
The plastic tip has been removed. the metal plunger is still intact. And both cylinders are reading 15-18% bypass with a leakdown tester both hot and cold. And the bypass air is coming from the crankcase, so just ring bypass lose. And adding a small amount of fresh fuel into the intake should eliminate fuel flow issues from the carb both still won't start.Well, first of all, all cutting the tip off a fuel solenoid does is make it a junk part.
Assuming the fuel dumped into the intake is actually making it to the cylinders, you likely have a sticking valve would be where I would check.
#4
T
txmowman
T
txmowman
As you know, the engine requires fuel, spark and compression. Since the engine ran previous, and given everything you wrote, it is either the coils or possibly the air gap.What the part number of the coils you received and what did you set the air gap to? Try moving the coils closer to the flywheel magnet, without them hitting of course, and retry.
#5
sgkent
sgkent
first thing I ask myself when troubleshooting an engine not starting, which is missing:
Air/Fuel
Spark
Compression
Others have said the same.
If all three are present, and there are no changes made like reversed plug wires or cam timing etc., then it may be flooded. If so why? Where is it coming from?
When a hot engine in summer floods, it can be from heat boiling the gasoline in the carb, which can be that the engine cooling is failing - especially on an air cooled engine, and it is running too hot.
One trick if you have spark and compression, and you think it might be flooded, is pull the apark plug and set it aside for a minute to dry. Pull the engine thru three or four times to clear out any excess fuel. Then put the plug back in and try it again. If it starts, that usually means it was flooded.
Air/Fuel
Spark
Compression
Others have said the same.
If all three are present, and there are no changes made like reversed plug wires or cam timing etc., then it may be flooded. If so why? Where is it coming from?
When a hot engine in summer floods, it can be from heat boiling the gasoline in the carb, which can be that the engine cooling is failing - especially on an air cooled engine, and it is running too hot.
One trick if you have spark and compression, and you think it might be flooded, is pull the apark plug and set it aside for a minute to dry. Pull the engine thru three or four times to clear out any excess fuel. Then put the plug back in and try it again. If it starts, that usually means it was flooded.
#6
R
Rivets
R
Rivets
Couple of things which come to my feeble mind. First, I checked the service manual and it calls for a Champion RCJ8Y plug. Second, I know you’ve done a leak down test, but I would perform a compression test, should have a minimum of 57 PSI. I wonder if it is different hot and cold. I know the oil pressure switch only triggers a warning light, but if I remember right I did have one that shorted out the ignition switch when it got hot. Replace it and problem went away that time. Manual says the fuel solenoid and pressure switch connect to the same terminal on the key switch. If that were the case I doubt you would hot spark. IL, I know you have been around the block at least one time, but I’ve got to ask a stupid question, please don’t be insulted. Have you checked for hot spark with an adjustable spark tester and can get it to jump at least 3/16”? I’ll keep thinking, keep us posted. I hope this is not a test, if so I failed.
#7
ILENGINE
ILENGINE
Coils are part number 21171-7034 set to .010. Standard is .008-.016.As you know, the engine requires fuel, spark and compression. Since the engine ran previous, and given everything you wrote, it is either the coils or possibly the air gap.What the part number of the coils you received and what did you set the air gap to? Try moving the coils closer to the flywheel magnet, without them hitting of course, and retry.
Even after adding fuel and cranking and then immediately removing plugs they are dry. Sometimes it will pop a couple times but still not start hot. Three different spark testers show spark. Something I may need to check but is unlikely an issue is partially sheared flywheel key but that condition on rider engines is rare unless some knothead removed the flywheel and didn't torque it properly. And most of the time a sheared flywheel on a rider engine is way out of time not just a few degrees.first thing I ask myself when troubleshooting an engine not starting, which is missing:
Air/Fuel
Spark
Compression
Others have said the same.
If all three are present, and there are no changes made like reversed plug wires or cam timing etc., then it may be flooded. If so why? Where is it coming from?
When a hot engine in summer floods, it can be from heat boiling the gasoline in the carb, which can be that the engine cooling is failing - especially on an air cooled engine, and it is running too hot.
One trick if you have spark and compression, and you think it might be flooded, is pull the apark plug and set it aside for a minute to dry. Pull the engine thru three or four times to clear out any excess fuel. Then put the plug back in and try it again. If it starts, that usually means it was flooded.
#8
T
txmowman
T
txmowman
Could be flooded, yes. But, heat is not likely the issue unless the routing of the fuel line has been changed from where MTD originally routed it. I still suspect the coils or if there is spark.
#9
ILENGINE
ILENGINE
Compression test not a bad idea even if just for reference.Couple of things which come to my feeble mind. First, I checked the service manual and it calls for a Champion RCJ8Y plug. Second, I know you’ve done a leak down test, but I would perform a compression test, should have a minimum of 57 PSI. I wonder if it is different hot and cold. I know the oil pressure switch only triggers a warning light, but if I remember right I did have one that shorted out the ignition switch when it got hot. Replace it and problem went away that time. Manual says the fuel solenoid and pressure switch connect to the same terminal on the key switch. If that were the case I doubt you would hot spark. IL, I know you have been around the block at least one time, but I’ve got to ask a stupid question, please don’t be insulted. Have you checked for hot spark with an adjustable spark tester and can get it to jump at least 3/16”? I’ll keep thinking, keep us posted. I hope this is not a test, if so I failed.
#10
T
txmowman
T
txmowman
This model does not use an oil pressure switch, at least not from Kawasaki.
Couple of things which come to my feeble mind. First, I checked the service manual and it calls for a Champion RCJ8Y plug. Second, I know you’ve done a leak down test, but I would perform a compression test, should have a minimum of 57 PSI. I wonder if it is different hot and cold. I know the oil pressure switch only triggers a warning light, but if I remember right I did have one that shorted out the ignition switch when it got hot. Replace it and problem went away that time. Manual says the fuel solenoid and pressure switch connect to the same terminal on the key switch. If that were the case I doubt you would hot spark. IL, I know you have been around the block at least one time, but I’ve got to ask a stupid question, please don’t be insulted. Have you checked for hot spark with an adjustable spark tester and can get it to jump at least 3/16”? I’ll keep thinking, keep us posted. I hope this is not a test, if so I failed.
#11
ILENGINE
ILENGINE
For a little more information If I replace the Champion RN14YC plugs with BPR5ES because I can't get the recommended BPR4ES it will start hot or cold. Or if I replace the hot Champion plugs with prior ran cold plugs will restart hot. 6 brand new plugs are failing hot.Could be flooded, yes. But, heat is not likely the issue unless the routing of the fuel line has been changed from where MTD originally routed it. I still suspect the coils or if there is spark.
#12
T
txmowman
T
txmowman
This model does not use an oil pressure switch, at least not from Kawasaki.
Couple of things which come to my feeble mind. First, I checked the service manual and it calls for a Champion RCJ8Y plug. Second, I know you’ve done a leak down test, but I would perform a compression test, should have a minimum of 57 PSI. I wonder if it is different hot and cold. I know the oil pressure switch only triggers a warning light, but if I remember right I did have one that shorted out the ignition switch when it got hot. Replace it and problem went away that time. Manual says the fuel solenoid and pressure switch connect to the same terminal on the key switch. If that were the case I doubt you would hot spark. IL, I know you have been around the block at least one time, but I’ve got to ask a stupid question, please don’t be insulted. Have you checked for hot spark with an adjustable spark tester and can get it to jump at least 3/16”? I’ll keep thinking, keep us posted. I hope this is not a test, if so I failed.
#13
T
txmowman
T
txmowman
Hot or cold plug would be no issue. The "heat range" is the plugs ability to remove heat from the cylinder. Not the actual "burn" of the fuel mixture.
#14
R
Rivets
R
Rivets
Sorry I posted the wrong plug number, NGK #BPR4ES or the Champion IL posted. About the oil pressure switch, doesn’t mean someone could have added one? Did come up with another stupid question. Have you tried to remove one or both of the kill wires, to see if you get a bang when hot?
#15
ILENGINE
ILENGINE
Actually as part of my testing have removed the kill wire one at a time and both at the same time. No change. Everything is leaning toward the new Champion plugs are shorting internally when hot. I could see a one doing it but 6.Sorry I posted the wrong plug number, NGK #BPR4ES or the Champion IL posted. About the oil pressure switch, doesn’t mean someone could have added one? Did come up with another stupid question. Have you tried to remove one or both of the kill wires, to see if you get a bang when hot?
#16
B
bertsmobile1
B
bertsmobile1
Well the closests to this I have come across was with a Toro Titan fitted with a Kohler
The first one did a similar thing and the quick & desperate solution was to slip some platinum plugs I had on hand for the LPG van .
Very embarassing as the customer came to collect, did a trial run up & down the front lawn, shut it down, paid the bill then it would not start to get put on the trailer
Mindful of that the other one they have I used the colortune on and it confirmed what I suspected when thinking about it latter on
The carb was just too lean so I drilled out the jets , next size up & problem vanished .
How ever in both cases it would restart on carb cleaner down the carb throat but not unassisted .
And FWIW I fitted platinum plugs to it as well
I really do not know the specific difference between an XC12YC & an RC12YC which is what I originally replaced the plugs with but nothing that specifies an XC plug will run properly on any other plug so I now keep XC's as well .
The first one did a similar thing and the quick & desperate solution was to slip some platinum plugs I had on hand for the LPG van .
Very embarassing as the customer came to collect, did a trial run up & down the front lawn, shut it down, paid the bill then it would not start to get put on the trailer
Mindful of that the other one they have I used the colortune on and it confirmed what I suspected when thinking about it latter on
The carb was just too lean so I drilled out the jets , next size up & problem vanished .
How ever in both cases it would restart on carb cleaner down the carb throat but not unassisted .
And FWIW I fitted platinum plugs to it as well
I really do not know the specific difference between an XC12YC & an RC12YC which is what I originally replaced the plugs with but nothing that specifies an XC plug will run properly on any other plug so I now keep XC's as well .
#17
StarTech
StarTech
You may have a carburetor problem. Try this the next time fails to start. Loosen the carburetor. Basically you to create an air gap between the carburetor and the intake manifold and see if the engine will fire up.
Just went something similar except it was a single barrel carburetor on a Honda engine. It was taking three pulls cold to start up but no matter how many times you pulled when hot it would not start. Since the carburetor was cheap from Honda I installed a new carb and everything worked as intended. One pull cold or hot would fire it up.
Now I assume I had a fuel leak of some kinda in carburetor but since I behind a few weeks here once the engine was running I when on to the next problem. Just was n't the time to explore a $15 carburetor problem.
Just went something similar except it was a single barrel carburetor on a Honda engine. It was taking three pulls cold to start up but no matter how many times you pulled when hot it would not start. Since the carburetor was cheap from Honda I installed a new carb and everything worked as intended. One pull cold or hot would fire it up.
Now I assume I had a fuel leak of some kinda in carburetor but since I behind a few weeks here once the engine was running I when on to the next problem. Just was n't the time to explore a $15 carburetor problem.
#18
ILENGINE
And something this is interesting, but may not meet peoples approval. Took my ohm meter and checked the resistance of the Champion both used in this engine and a new RN14YC plug. And compared it to the NGK both new and the plugs that are currently installed. The Champion plugs that were used are reading 12-15M ohms. The new Champion RN14YC plug is reading 83k ohms. The NGK both new and used in this engine are testing around 5k ohms.
ILENGINE
Compression around 105-110 on both cylinders on a warm but not hot engine. Ran a couple minutes and then pulled the plugs.Second, I know you’ve done a leak down test, but I would perform a compression test, should have a minimum of 57 PSI. I wonder if it is different hot and cold.
And something this is interesting, but may not meet peoples approval. Took my ohm meter and checked the resistance of the Champion both used in this engine and a new RN14YC plug. And compared it to the NGK both new and the plugs that are currently installed. The Champion plugs that were used are reading 12-15M ohms. The new Champion RN14YC plug is reading 83k ohms. The NGK both new and used in this engine are testing around 5k ohms.
#19
R
Rivets
R
Rivets
I haven’t seen an entire box of Champion plugs bad since the early 80’s. Now you are starting to fry my brain! To me nothing is making sense. At this point, if I had this engine, I would run the NGK BPR5ES plugs until it gets HOT. Then I would look at the plugs. If the plug has a little black tint to it I would run those plugs. If the porcelain is bright white, I would say those plugs are too hot and I’m back to square one. Just my opinion, but read my signature.
#20
ILENGINE
I have a similar engine in the shop right now that takes the same plug. I may pull the plugs out of it and then run it and see if I can duplicate the no start engine with the suspected faulty plugs.
Just tried resetting the air gap on the modules from 010 to .014 and tried the Champion plugs again. Started cold but would only pop but not start hot. Dropped the NGK back in it and fired right off.
ILENGINE
Already had done that before you even commented. The BPR5ES have slightly darkened porcelains after having put about half an hour on them. This sets up the issue that I use the Champion plugs and the customer starts the mower and mowers their entire yard before shutting off will never see the plug issue. The ones that mow for a period and then shut off the mower to go get a drink and come back will have a no start.I haven’t seen an entire box of Champion plugs bad since the early 80’s. Now you are starting to fry my brain! To me nothing is making sense. At this point, if I had this engine, I would run the NGK BPR5ES plugs until it gets HOT. Then I would look at the plugs. If the plug has a little black tint to it I would run those plugs. If the porcelain is bright white, I would say those plugs are too hot and I’m back to square one. Just my opinion, but read my signature.
I have a similar engine in the shop right now that takes the same plug. I may pull the plugs out of it and then run it and see if I can duplicate the no start engine with the suspected faulty plugs.
Just tried resetting the air gap on the modules from 010 to .014 and tried the Champion plugs again. Started cold but would only pop but not start hot. Dropped the NGK back in it and fired right off.